"We will fight against terror until the very end in the name of humanity," he added.

With a population of almost two million, Adana is one of Turkey's largest cities, lying around 100 kilometres (60 miles) from the Syrian border.

The US consulate in Adana in September had warned its citizens of a potential security threat targeting US-branded hotels there.

Incirlik air base, located just outside Adana, is used by American and coalition forces as a hub for air raids against Islamic State (IS) jihadists in neighbouring Syria.

Turkey has already been hit by a bloody year of militant attacks in its two biggest cities that have left dozens of people dead and put the country on a high security alert.

Kurdish militants have twice struck in Ankara in deadly attacks, while suspected IS suicide bombers have hit Istanbul on three occasions.

In June, 47 people were killed in a triple suicide bombing and gun attack at Istanbul's Ataturk airport, with authorities pointing the finger at IS.

Fifty-seven people, 34 of them children, were killed in August in a suicide attack carried out by a bomber linked to IS jihadists at a Kurdish wedding in the southeastern city of Gaziantep.

The country is also still reeling from a failed 15 July coup blamed on the US-based Islamic preacher Fethullah Gulen that has been followed by a relentless purge of his supporters from all state institutions.

Battle against PKK

There was no immediate indication who could be behind the latest attack.

The Turkish military has stepped up operations against Kurdish militants after a fragile ceasefire broke down in 2015. There has been a dramatic surge in violence that so far shows no sign of ending.

The outlawed Kurdistan Workers' Party (PKK), designated as a terror group by Turkey and its Western allies, generally concentrates its attacks in the southeast of the country.

While it is located strategically in southern Turkey, Adana lies to the west of the southeastern region that has been the main theatre of conflict with the PKK.